Climate change is coming for humanity as its “greatest threat in thousands of years,” says Sir David Attenborough.

The famed British broadcaster and historian, 92, offered the harsh warning at the opening ceremony of climate talks in Poland sponsored by the United Nations.

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“Right now, we are facing a man-made disaster of global scale. Our greatest threat in thousands of years. Climate change,” he said. “If we don’t take action, the collapse of our civilizations and the extinction of much of the natural world is on the horizon. . . . The message is clear: Time is running out.”

Attenborough also praised the Paris Agreement, which was established in 2015 and aims to keep global warming at less than 3.6 degrees Fahrenheit above preindustrial levels over the next century.

“The UN provides a unique platform that can unite the whole world, and, as the Paris Agreement proved, together we can make real change happen,” he said.

The BBC reports that Attenborough is in attendance at the meetings to take “the People’s Seat,” meaning he’ll act as a liaison between policymakers and regular folk during the talks.

UN Secretary General Antonio Guterres also spoke Monday, and reminded world leaders to take global warming seriously, as it’s the “most important issue we face.”

“Even as we witness devastating climate impacts causing havoc across the world, we are still not doing enough, nor moving fast enough, to prevent irreversible and catastrophic climate disruption,” he said.

Guterres, who assumed his position last year, also claimed that not enough has been done to back the Paris Agreement, and urged countries to cut their emissions by 45% from 2010 levels by 2030, with the hopes of net zero emissions by 2050.

President Trump announced his intentions to leave the Paris deal in June 2017, claiming it “demeaned” the United States.

In response, a group of state governors, including New York’s Andrew Cuomo, teamed up to form the United States Climate Alliance, which works to keep at the objectives of the Paris Agreement at the state level.